There is a hidden overflow condition there. As date is signed
and u8 is unsigned, doing:
date = (data[0] << 24)
With a value bigger than 07f will make all upper bits of date
0xffffffff. This can be demonstrated with this small code:
<code>
typedef int64_t time64_t;
typedef uint8_t u8;
int main(void)
{
u8 data[] = { 0xde ,0xad , 0xbe, 0xef };
time64_t date;
date = (data[0] << 24) | (data[1] << 16) | (data[2] << 8) | data[3];
printf("Invalid data = 0x%08lx\n", date);
date = ((unsigned)data[0] << 24) | (data[1] << 16) | (data[2] << 8) | data[3];
printf("Expected data = 0x%08lx\n", date);
return 0;
}
</code>
Fix it by converting the upper bit calculation to unsigned.
Fixes: cea28e7a55e7 ("media: pulse8-cec: reorganize function order")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@xxxxxxxxxx>
---
drivers/media/cec/usb/pulse8/pulse8-cec.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/media/cec/usb/pulse8/pulse8-cec.c b/drivers/media/cec/usb/pulse8/pulse8-cec.c
index ba67587bd43e..171366fe3544 100644
--- a/drivers/media/cec/usb/pulse8/pulse8-cec.c
+++ b/drivers/media/cec/usb/pulse8/pulse8-cec.c
@@ -685,7 +685,7 @@ static int pulse8_setup(struct pulse8 *pulse8, struct serio *serio,
err = pulse8_send_and_wait(pulse8, cmd, 1, cmd[0], 4);
if (err)
return err;
- date = (data[0] << 24) | (data[1] << 16) | (data[2] << 8) | data[3];
+ date = ((unsigned)data[0] << 24) | (data[1] << 16) | (data[2] << 8) | data[3];
dev_info(pulse8->dev, "Firmware build date %ptT\n", &date);
dev_dbg(pulse8->dev, "Persistent config:\n");
--
2.47.0
